From 0e37f70a58d512858b38e1458c6d83bc1727269c Mon Sep 17 00:00:00 2001
From: Michael Orlitzky <michael@orlitzky.com>
Date: Tue, 31 Dec 2013 21:07:31 -0500
Subject: [PATCH] Add code to main to delete successfully imported files.

---
 src/Main.hs         | 69 ++++++++++++++++++++++++++++++++++-----------
 src/TSN/XML/News.hs |  4 +--
 2 files changed, 55 insertions(+), 18 deletions(-)

diff --git a/src/Main.hs b/src/Main.hs
index 3ea2606..9a95321 100644
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -1,8 +1,11 @@
 {-# LANGUAGE NoMonomorphismRestriction #-}
+{-# LANGUAGE DoAndIfThenElse #-}
 module Main
 where
 
 import Control.Arrow ( (&&&), arr, returnA )
+import Control.Concurrent ( threadDelay )
+import Control.Exception ( SomeException, catch )
 import Control.Monad ( when )
 import Control.Monad.IO.Class ( MonadIO, liftIO )
 import Database.Groundhog.Generic ( runDbConn )
@@ -13,6 +16,7 @@ import Database.Groundhog.Postgresql (
 import Data.Monoid ( (<>) )
 import Network.Services.TSN.Logging ( init_logging )
 import System.Console.CmdArgs ( def )
+import System.Directory ( removeFile )
 import System.Exit ( exitWith, ExitCode (ExitFailure) )
 import System.IO.Error ( catchIOError )
 import Text.XML.HXT.Core (
@@ -46,27 +50,31 @@ import Xml ( parse_opts )
 
 
 
-import_file :: Configuration -> FilePath -> IO ()
+import_file :: Configuration -> FilePath -> IO Bool
 import_file cfg path = do
-  results <- catchIOError
-               parse_and_import
-               (\e -> do
-                  report_error (show e)
-                  report_error $ "Failed to import file " ++ path ++ "."
-                  -- Return a nonempty list so we don't claim incorrectly that
-                  -- we couldn't parse the DTD.
-                  return [ Nothing ] )
-
+  results <- parse_and_import `catch` exception_handler
   case results of
     -- If results' is empty, one of the arrows return "nothing."
-    []    -> report_error $ "Unable to determine DTD for file " ++ path ++ "."
+    []    -> do
+      report_error $ "Unable to determine DTD for file " ++ path ++ "."
+      return False
     (r:_) ->
       case r of
-        Nothing -> return ()
-        Just cnt -> report_info $ "Successfully imported " ++
-                                  (show cnt) ++
-                                  " records from " ++ path ++ "."
+        Nothing -> return False
+        Just cnt -> do
+          report_info $ "Successfully imported " ++
+                          (show cnt) ++
+                          " records from " ++ path ++ "."
+          return True
   where
+    exception_handler :: SomeException -> IO [Maybe Int]
+    exception_handler e = do
+      report_error (show e)
+      report_error $ "Failed to import file " ++ path ++ "."
+      -- Return a nonempty list so we don't claim incorrectly that
+      -- we couldn't parse the DTD.
+      return [Nothing]
+
     -- | An arrow that reads a document into an 'XmlTree'.
     readA :: IOStateArrow s a XmlTree
     readA = readDocument parse_opts path
@@ -142,4 +150,33 @@ main = do
 
   -- We don't do this in parallel (for now?) to keep the error
   -- messages nice and linear.
-  mapM_ (import_file cfg) (OC.xml_files opt_config)
+  results <- mapM (import_file cfg) (OC.xml_files opt_config)
+
+  -- Zip the results with the files list to find out which ones can be
+  -- deleted.
+  let result_pairs = zip (OC.xml_files opt_config) results
+  let victims = filter (\(_,result) -> result) result_pairs
+  mapM_ ((kill True) . fst) victims
+
+  where
+    kill try_again path = do
+      removeFile path `catchIOError` exception_handler
+      report_info $ "Removed imported file " ++ path ++ "."
+      where
+        -- | A wrapper around threadDelay which takes seconds instead of
+        --   microseconds as its argument.
+        thread_sleep :: Int -> IO ()
+        thread_sleep seconds = do
+          let microseconds = seconds * (10 ^ (6 :: Int))
+          threadDelay microseconds
+
+        exception_handler :: IOError -> IO ()
+        exception_handler e = do
+          report_error (show e)
+          report_error $ "Failed to remove imported file " ++ path ++ "."
+          if try_again then do
+            report_info $ "Waiting 5 seconds to attempt removal again..."
+            thread_sleep 5
+            kill False path
+          else
+            report_info $ "Giving up on " ++ path ++ "."
diff --git a/src/TSN/XML/News.hs b/src/TSN/XML/News.hs
index 5782d24..550f26c 100644
--- a/src/TSN/XML/News.hs
+++ b/src/TSN/XML/News.hs
@@ -86,7 +86,7 @@ instance ToFromXml NewsTeam where
   -- used our named fields.
   to_xml (NewsTeam {..}) = NewsTeamXml db_team_name
   -- We can't create a DefaultKey Message...
-  from_xml = error "Called from_xml on a NewsTeam"
+  from_xml = error "Called from_xml on a NewsTeam."
   -- unless we're handed one.
   from_xml_fk key = (NewsTeam key) . xml_team_name
 
@@ -124,7 +124,7 @@ instance ToFromXml NewsLocation where
   -- used our named fields.
   to_xml (NewsLocation {..}) = NewsLocationXml db_city db_state db_country
   -- We can't create a DefaultKey Message...
-  from_xml = error "Called from_xml on a NewsLocation"
+  from_xml = error "Called from_xml on a NewsLocation."
   -- unless we're given one.
   from_xml_fk key (NewsLocationXml x y z) = NewsLocation key x y z
 
-- 
2.44.2